How are monoterpenes different from sesquiterpenes?

Monoterpenes and sesquiterpenes are both classes of isoprenoids, which are organic compounds built from five-carbon isoprene units. They differ primarily in their molecular size, composition, and physical properties:

• Molecular Composition: Monoterpenes consist of two isoprene units, resulting in a molecular formula of $C_{10}{H}_{16}$. Sesquiterpenes are larger, containing three isoprene units, which gives them a molecular formula of $C_{15}{H}_{24}$.12
• Volatility: Monoterpenes are generally volatile oils, which contributes to their characteristic fragrances. Sesquiterpenes have a lower volatility than monoterpenes.345
• Structural Complexity: While both classes exhibit diverse structures—including acyclic, monocyclic, and bicyclic forms—sesquiterpenes demonstrate an even greater complexity of structure than monoterpenes.15
• Isolation and Use: Monoterpenes are typically isolated via steam distillation. Because of their lower volatility, sesquiterpenes are often isolated through extraction or steam distillation and purified using chromatography or vacuum fractional distillation. While monoterpenes are widely used as flavorings and solvents, sesquiterpenes also contribute to the flavors of various foods.453